Coating mechanism for lamp filaments



March 8, 1955 T. HAMILTON 2,703,552 COATING MECHANISM FOR LAMP FILAMENTS} Filed April ,27, 1953 2 Sheets-Sheet l INVENTOR. Thomas 111022412021 March 8, 1955 T. HAMILTON 2,703,552

COATING MECHANISM FOR LAMP FILAMENTS Filed April 27, 1953 2 Sheets-Sheet 2 1.9 INVENTOR.

Thoma/s fiamdion United States PatentO 2,703,552 COATING MECHANISM FOR LAMP FILAMENTS Thomas Hamilton, Verona, N. J., assignor to Westinghouse Electric Corporation, a corporation of Pennsylvama Application April 27, 1953, Serial No. 351,385 2 Claims. (Cl. 118-612) This invention relates to coating mechanisms, and more particularly, to apparatus for applying a coating, for instance, of gettering material, to a lamp filament in the course of manufacture of an incandescent lamp. The invention, however, is not necessarily confined to this arbitrarily selected use.

In the lamp industry, one of the final steps in process of manufacture employed in connection with the stem assembly before sealing the same within its bulb, is to apply a coating of gettering material to the filament. Uniformity of application and constituency of the gettering material on the filament are important considerations which have presented difliculties in prior art practice. The gettering material, due to its considerable viscosity is slow flowing, and as it is a mixture in which one ingredient is a metallic powder or fine granules carried in suspension, there is serious difliculty with settling thereof in the fluid carrier ingredient. As a consequence, the proportion of the powder or granule ingredient applied to successively treated filaments has varied considerably in the past.

According to the present invention, I propose a structure of coating mechanism which will be consistent in the coating applied to successively treated filaments.

An essential object of the invention is to maintain an even distribution of the comminuted ingredient in the mixture during operation of the machine.

Another object of the invention is to utilize the applicator means to also keep the mixture in constant condition of ingredient distribution.

A further object of the invention is to disrupt any accumulation of a settling ingredient.

More specifically, the invention has an objective of applying agitation to the mixture in the region where settling is most prevalent.

Other objects, advantages and beneficial results will become apparent to persons skilled in the art to WhlCh the invention appertains as the description proceeds, both by direct reference thereto and by implicatlon from the context.

Referring to the accompanying drawings, 1n which like numerals of reference indicate similar parts throughout the several views:

Figure 1 is a sectional elevation of a coating mechamsm in position coating a filament;

Figure 2 is a perspective view of a lamp havmg a filament of the character shown in Fig. 1;

Figure 3 is a plan of the mechamsm as v1ewed from line IIIIII of Fig. 1;

Figure 4 is a sectional view s1m1lar to and showmg a portion of the mechanism of Fig. l at a dlflerent part of the cycle of operation; and

Figure 5 is a cross-section on l1ne Y-V of F g. 4.

In the specific embodiment of the mventlon lllustrated in said drawing, the mechanism in its general aspect comprises a reservoir for the coating mixture 11, a portion of the mixture being lifted up by a dipper 12 each time the machine indexes a stem assembly 13 over the reservoir, said stem assembly being carried on the travelling head of the machine by a clamp or holder 14. It will be understood that the stem assembly includes a flare 15 at an end of the glass tubular stem 16 and that a tubulation 17 extends from within the stem outwardly hrough the flare, and it is this extended part of the :ubulation as shown in the drawing which is gripped by :lamp or holder 14. As located for the coating opera- ;ion, the filament 18, which may be considered m a gen- 2,703,552 Patented Mar. 8, 1955 eral aspect as a workpiece, is directed downwardly and the tubulation projects upwardly. Furthermore, during the coating operation, the filament and the reservoir both are stationary with the filament suspended above the reservoir and the dipper 12 rises to immerse the filament in the coating mixture contained in the dipper.

The reservoir 10 is mounted in fixed position from the frame of the machine as by a post 19 projecting from the bottom of the reservoir and supported in a bracket 20 on the machine. Centrally within the reservoir extending upright from the bottom thereof, is a cylinder 21 which is completely submerged in the supply of coating mixture. Apertures 22 are provided at the bottom of this cylinder opening from the interior to the exterior of the cylinder and thereby providing communication for the mixture to pass to and from the interior of the cylinder from and to the bottom of the reservoir. Said apertures are shown as long slots in circumferential disposition to the cylinder. The upper end of the cylinder is fully open except as it may be closed during operation by entry of a plunger therein as described hereinbelow.

The dipper 12 has a central depending appendage which essentially constitutes a plunger 23 the diameter of which is appropriate for entry into cylinder 21. The length of the plunger is likewise proportioned so that it may be depressed into the cylinder substantially as far as the apertures 22 thereof. The upper part of the dipper above the plunger is shown larger than the plunger and has an interior cavity 24 fully open at its top and tapering at its bottom toward the axis of the plunger where an outlet channel 25 is provided downwardly within the plunger and sloping to one side thereof so as to provide a discharge outlet 26 at the side of said plunger.

Any suitable supporting and operating means may be provided to raise and lower the dipper in timed relation to the indexing of the machine, and as one exemplification I have shown an upwardly projecting arm 27 at one side of the dipper which is carried near its top in a bracket 28 extending thereto from a vertically reciprocating carriage 29. Said carriage is secured at the upper end of a reciprocating rod 30 which extends into the machine and is appropriately operated by a cam (not shown) or other means in timed relation with the indexing of the machine. The carriage 29 has yokes 31 integral therewith and forming a guideway spanning a guide-rod or track 32 supported from the machine by a bracket 33. The arrangement is such that the carriage can neither tilt nor rotate and has longitudinal movement only. It thus provides a proper support for the dipper so that the plunger 23 of the dipper is always in coaxial alignment with cylinder 21. By virtue of this construction, the plunger may be raised out of the cylinder and will accurately return into the same when subsequently lowered.

In operation, the dipper is adapted to be entirely submerged below the surface of the fluid or mixture 11 when the dipper and plunger are in the lowermost position. This aifords opportunity for the fluid to entirely fill the dipper which is thereafter raised to a position where the fluid level is above filament 18 of the stem assembly 13 which has been brought to to raising of the dipper. in the pool of coating mixture in the dipper accordingly applies coating of that material thereon which is retained thereby when the dipper is lowered. It will be understood that these operations continue in sequence on one filament after another which arrive in the indexed position over the reservoir and dipper. As the opening 26 at the side of the plunger rises above the level of the fluid 11 in the reservoir, when the dipper is in its raised position, some of the contents of the dipper will flow back into the reservoir, but due to the viscosity of the fluid mixture, the discharge from the dipper is relatively slow and the surface level of the fluid in the dipper is well above the filament when the dipper is in its raised position during normal sequence of operation of the machine. The discharge of fluid from the bottom of the dipper is desired so as to constantly replenish the contents of the dipper and to drain off the bottom layers of the fluid from the dipper which otherwise might become the indexed position just prior This immersion of the filament thiclgened with precipitation or settling of heavy particles carried in suspension therein. The arrangement is accordingly such that the consistency of the fluid in the dipper is kept constant and as a result, the successive filaments coated by the machine will have the identical amount of character of coating thereon.

As the dipper is lowered, plunger 23 thereof enters cylinder 21 and forcibly ejects fluid content thereof out through the apertures 22, creating a turbulence in the bottom of the reservoir and therefore returns settling particles back into suspension in the fluid, keeping the fluid and particles mixed and preventing precipitation and accumulation of particles at the bottom of the reservoir. I accordingly have provided a simple and rugged means which not only maintains a constant characterization of fluid throughout the reservoir, but also .maintains the fluid of the same characterization constantly in the dipper as presented at the filament for coating the same.

The mixture coated on the filament in the case of electric lamps is generally for the purpose of gettering, and thus after the stem has been sealed in its bulb 34, current is applied through the usual lead connections 35 to the filament and the heat from the filament affects the applied coating, which, being of gettering material, reduces certain undesirable gaseous contents of the bulb and improves the evacuated condition of the lamp as will be understood by persons conversant with the art.

I claim:

1. A coating mechanism comprising, a reservoir, a dipper movable into and out of the reservoir for lifting a part of the contents thereof for operative presentation to a workpiece, and telescoping members of which one member is movable and the other stationary and of which the movable member is carried by and movable with the dipper, said members beingconstituted as a cooperating plunger and cylinder with an outlet leading from the interior of the cylinder and opening laterally into the region next to the bottom of the reservoir for ejecting contents of the cylinder as the plunger telescopes therein, thereby forcibly pumping the liquid laterally into the reservoir and creating a flow over the bottom of said reservoir of substantially the entire contents of the cylinder for preventing accumulation of precipitate.

2'. A coating mechanism comprising, a reservoir having an upright cylinder therein, said cylinder having apertures next to its bottom opening into the reservoir, a dipper reciprocable coaxially to said cylinder and movable into and out of the reservoir for lifting a part of the contents of the reservoir for operative presentation to a workpiece, and a plunger on said dipper coaxial to said cylinder and movable thereinto while the dipper submerges in the reservoir, said plunger forcing the cylinder contents out of said apertures into said reservoir.

References Cited in the file of this patent UNITED STATES PATENTS 1,010,594 Cowles Dec. 5, 1911 1,789,309 Herrick Jan. 20, 1931 2,422,457 Zabel June 17, 1947 2,432,081 Bartholomew Dec. 9, 1947 2,545,909 Zabel Mar. 20, 1951 

